auto number depending on the last record created

auto number depending on the last record created

Hi, I want to use the Auto number filed in C5 but the problem is that my number I want to auto create has to have a letter and -.

I have a list of project. Each project has a number like P-18-0200. When I create another project, I want the filed "Project number" in my form to be autopopulated with the last project number + 1.

Ex: Last project number was P-18-0150, so the next number should be P-18-0151.

How can I do that?

Thnak guys!